U.S. patent application number 10/996490 was filed with the patent office on 2005-06-30 for method for monitoring a component situated in an exhaust gas region of an internal combustion engine.
Invention is credited to Handler, Torsten, Mueller, Klaus, Ripper, Wolfgang, Samuelsen, Dirk, Wickert, Stefan.
Application Number | 20050143897 10/996490 |
Document ID | / |
Family ID | 34609480 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050143897 |
Kind Code |
A1 |
Ripper, Wolfgang ; et
al. |
June 30, 2005 |
Method for monitoring a component situated in an exhaust gas region
of an internal combustion engine
Abstract
A method for monitoring a component situated in an exhaust gas
region of an internal combustion engine in which the low pass
behavior, which is determined by the heat capacity of the
component, is monitored by a valuation of a measure of a first
exhaust gas temperature, which appears upstream of the component
that is to be monitored, and of a second exhaust gas temperature,
which is recorded by a second temperature sensor downstream from
the component to be monitored.
Inventors: |
Ripper, Wolfgang;
(Stuttgart, DE) ; Wickert, Stefan; (Albershausen,
DE) ; Handler, Torsten; (Stuttgart, DE) ;
Samuelsen, Dirk; (Ludwigsburg, DE) ; Mueller,
Klaus; (Tamm, DE) |
Correspondence
Address: |
KENYON & KENYON
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
34609480 |
Appl. No.: |
10/996490 |
Filed: |
November 24, 2004 |
Current U.S.
Class: |
701/101 ;
701/108 |
Current CPC
Class: |
F01N 2550/02 20130101;
F01N 11/002 20130101; F01N 2900/0422 20130101; Y02T 10/47 20130101;
Y02T 10/40 20130101 |
Class at
Publication: |
701/101 ;
701/108 |
International
Class: |
G06F 019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 12, 2003 |
DE |
10358195.2 |
Claims
What is claimed is:
1. A method for monitoring a component situated in an exhaust gas
region of an internal combustion engine, the method comprising:
ascertaining a measure for a first exhaust gas temperature upstream
of the component; measuring a second exhaust gas temperature by a
second temperature sensor, which occurs downstream from the
component; checking a low pass behavior, which is determined by a
heat capacity of the component, by a valuation of the first exhaust
gas temperature with respect to the second exhaust gas temperature;
and emitting an error signal in response to a change of a
predefined measure for the low pass behavior of the component.
2. The method according to claim 1, further comprising calculating
the measure for the first exhaust gas temperature using a model of
exhaust gas, in which at least one of a fuel signal, an air-mass
signal and an air quantity flow signal of the engine is taken into
consideration.
3. The method according to claim 1, wherein at least one of a
torque and a load of the engine is used as a measure for the first
exhaust gas temperature.
4. The method according to claim 1, further comprising providing a
low pass filtering of the first exhaust gas temperature and
subsequently a difference formation from the second exhaust gas
temperature.
5. The method according to claim 1, further comprising providing a
formation of a tolerance band about the first exhaust gas
temperature and a subsequent difference formation between the
tolerance band and the second exhaust gas temperature.
6. The method according to claim 1, further comprising providing a
gradient formation of the first and second exhaust gas temperatures
and a subsequent valuation of the gradients.
7. The method according to claim 6, further comprising providing an
ascertainment of a time difference between at least one of maxima
and minima between the two gradients of the first and second
exhaust gas temperatures.
8. The method according to claim 1, further comprising providing at
least one of (a) an amplitude comparison between the first and
second exhaust gas temperatures and (b) an amplitude comparison of
gradients of the first and second exhaust gas temperatures in a
predefined time interval.
9. The method according to claim 1, further comprising providing a
spectral analysis of the first and second exhaust gas
temperatures.
10. The method according to claim 1, further comprising providing a
correlation of the first exhaust gas temperature to the second
exhaust gas temperature.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for monitoring a
component situated in an exhaust gas region of an internal
combustion engine, in which a measure is ascertained for a first
exhaust gas temperature that appears upstream of the component, and
in which a second exhaust gas temperature is measured which appears
downstream from the component.
BACKGROUND INFORMATION
[0002] German Patent Application No. DE 44 26 020 describes a
method, in which the operativeness of a catalytic converter, that
is situated in the exhaust gas region of an internal combustion
engine, is monitored. The monitoring is performed with the aid of
the temperature increase generated by an exothermic reaction of the
exhaust gases in the catalytic converter. Two temperature signals
are ascertained, the first temperature signal being based on a
measurement of the temperature downstream from the catalytic
converter, and the second temperature signal being calculated with
the aid of a model.
[0003] The present invention is based on the object of providing a
method for monitoring a component situated in the exhaust gas
region of an internal combustion engine, which makes possible
making a statement concerning a change in the component.
SUMMARY OF THE INVENTION
[0004] According to the present invention, monitoring the thermal
low pass behavior of the component is provided, which is determined
by the heat capacity of the component. The monitoring takes place
by a valuation of the first exhaust gas temperature that occurs
upstream of the component, with respect to the second exhaust gas
temperature, which is measured downstream from the component. In
response to a change of a predefined measure of the thermal low
pass behavior of the component, an error signal is emitted.
[0005] The method according to the present invention makes possible
monitoring of the component for a change which may have taken
place, for example, during an inadmissible manipulation. In the
extreme case, the component to be monitored, such as a catalytic
converter and/or a particulate filter, may have been completely
removed. The thermal low pass behavior of the component to be
monitored is determined by its heat capacity. The concepts "heat
capacity" and "thermal low pass behavior" are mutually
interchangeable. Only the concept of thermal low pass behavior is
still used below.
[0006] For the components to be monitored, the predefined measure
for the thermal low pass behavior may be either calculated or
ascertained experimentally.
[0007] The method according to the present invention makes possible
a simple monitoring of the components situated in the exhaust gas
region of the internal combustion engine, either within the scope
of controls, which have to be carried out with respect to keeping
up exhaust gas norms, or during normal operation.
[0008] The measure for the first exhaust gas temperature, which
corresponds to the exhaust gas temperature upstream of the
component to be monitored, may be calculated instead of a
measurement, preferably in the light of an exhaust gas model. The
first exhaust gas temperature may be calculated from quantities,
such as rotary speed and torque, or rotary speed and metered fuel
rate, which are present in an engine control.
[0009] A first embodiment of the method according to the present
invention provides a low pass filtering of the variation with time
of the first exhaust gas temperature, and a subsequent difference
formation from the variation with time of the second exhaust gas
temperature. The time constant of the low pass filtering should be
approximately set to the expected value of the component to be
monitored. Exceeding a predefined threshold or leaving a threshold
band upwards or downwards of the difference indicates that a change
has occurred in the thermal low pass behavior.
[0010] Another embodiment of the method according to the present
invention provides the formation of a tolerance band about the
first exhaust gas temperature, and subsequently a difference
formation of the boundaries of the tolerance band from the second
exhaust gas temperature. The tolerance band about the first exhaust
gas temperature is formed by adding a predefined amount to the
current exhaust gas temperature value, and by subtracting an also
predefined amount. The spread of the tolerance band may be
calculated or determined experimentally. The difference formation
from the second exhaust gas temperature and the comparison of the
difference to a predefined threshold value or threshold band makes
possible the statement on the change in the thermal low pass
behavior.
[0011] Another embodiment of the method according to the present
invention provides a gradient formation of the variation with time
of the exhaust gas temperatures as well as a subsequent valuation
of the gradient. The gradient formation makes possible the simple
ascertainment of signal maxima or signal minima. In one further
development, in order to ascertain the low pass behavior, an
evaluation of the time difference between two temperature maxima
and/or temperature minima may be provided. One other embodiment
within the scope of gradient formation provides a comparison of the
gradients of the temperature variation.
[0012] Still another embodiment of the method according to the
present invention provides an amplitude comparison between the
first and second exhaust gas temperature. Based on the low pass
behavior of the component to be monitored, smaller amplitudes come
about for the second exhaust gas temperature than for the first
exhaust gas temperature. By making a comparison to a predefined
threshold value or threshold band for the two ascertained
amplitudes, it is possible to monitor the thermal low pass
behavior.
[0013] Still another embodiment of the method according to the
present invention provides a spectral analysis of the variation
with time of the first and second exhaust gas temperature. Based on
the low pass behavior of the component to be monitored, the center
of gravity of the spectral lines or of the continuum shift starting
from higher frequency portions for the first exhaust gas
temperature to the lower frequency portions for the second exhaust
gas temperature. For example, the thermal low pass behavior may be
monitored by forming the center of gravity of the envelope of the
two spectral curves, and by making a comparison to a predefined
threshold value or threshold band.
[0014] Still another embodiment of the method according to the
present invention provides a correlation of the second exhaust gas
temperature to the first exhaust gas temperature. The correlation
is a mathematical operation which gives a higher numerical value
for correlating exhaust gas temperatures than for deviating ones. A
high value of the correlation accordingly shows a reduced low pass
behavior.
[0015] A further refinement provides that the measure for the first
exhaust gas temperature is given by a load signal and/or a torque
of the internal combustion engine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a technical environment in which a method
according to the present invention runs.
[0017] FIG. 2 shows exhaust gas temperatures as a function of
time.
DETAILED DESCRIPTION
[0018] FIG. 1 shows an internal combustion engine 10 having an
intake region and an exhaust gas region 11, 12. In intake region 11
there is situated an air-mass flow sensor or an air quantity flow
sensor 13, which emits an air-mass signal or an air quantity flow
signal mL to engine control 14. In exhaust gas region 12 there is
situated a lambda sensor 15, which emits a lambda signal LAM to
engine control 14. Engine control 14 ascertains from air-mass
signal mL, from lambda signal LAM and from an accelerator signal
PWG, which is made available by a gas pedal 16, a fuel signal ME,
which is a measure of the fuel quantity supplied to internal
combustion engine 10.
[0019] A rotary speed signal N is also supplied to engine control
14.
[0020] Fuel signal ME and rotary speed signal N are additionally
conducted to a monitoring device 17, which monitors a component 18
situated in exhaust gas region 12. Upstream of component 18 that is
to be monitored, a first temperature sensor TV is situated which
emits a first temperature signal TvK to monitoring device 17.
Downstream from component 18 that is to be monitored, a second
temperature sensor TH is situated, which emits a second temperature
signal TnK to monitoring device 17. From the comparison of signals
to threshold values, which are stored in a threshold value memory
18, monitoring device 17, if necessary, emits an error signal
FS.
[0021] FIG. 2 shows the first and the second exhaust gas
temperatures TvK, TnK as a function of time t. First exhaust gas
temperature TvK has more changes with respect to time than second
exhaust gas temperature TnK. In addition, first exhaust gas
temperature TvK has a greater amplitude with respect to predefined
time intervals than second exhaust gas temperature TnK.
[0022] The device shown in FIG. 1 operates as follows:
[0023] Engine control 14 ascertains fuel signal ME, which forms the
basis for metering fuel to internal combustion engine 10, as a
function of air quantity signal mL, of accelerator signal PWG, of
rotary speed N and of lambda signal LAM. Component 18, that is to
be monitored, is situated in exhaust gas region 12 of internal
combustion engine 10. Component 18 may be, for example, a catalytic
converter or, for instance, a particulate filter.
[0024] First temperature sensor TV records first exhaust gas
temperature TvK, which appears upstream of component 18 that is to
be monitored. Second temperature sensor TH records second exhaust
gas temperature TnK, which appears downstream from component 18
that is to be monitored.
[0025] The method according to the present invention for monitoring
component 18 that is situated in exhaust gas region 12 of internal
combustion engine 10 is based on checking the thermal low pass
behavior of component 18 that is to be monitored, which occurs
based on its heat capacity.
[0026] The method according to the present invention starts from
the fact that second exhaust gas temperature TnK is constantly
recorded by an actually present temperature sensor, by second
temperature sensor TH in the exemplary embodiment. First exhaust
gas temperature TvK may be recorded by a temperature sensor, in the
exemplary embodiment shown, by first temperature sensor TV.
Alternatively or additionally, calculation of first exhaust gas
temperature TvK is provided, using a model of the exhaust gas.
Using the model included in monitoring device 17, a measure for
first exhaust gas temperature TvK may be ascertained, for instance,
from rotary speed N and fuel signal ME. If necessary, for example,
air-mass signal or air quantity flow signal mL may be drawn upon
additionally or alternatively to fuel signal ME.
[0027] The measure for first exhaust gas temperature TvK may also
be given only by fuel signal ME or by air-mass signal or air
quantity flow signal mL or by accelerator signal PWG in conjunction
with rotary speed signal N, corresponding to the torque or the load
of internal combustion engine 10, since the torque and the load
mirror first exhaust gas temperature TvK.
[0028] A first embodiment of the method according to the present
invention provides a low pass filtering of first exhaust gas
temperature TvK, and a subsequent difference formation from second
exhaust gas temperature TnK. The low pass behavior of component 18
that is to be monitored may be indicated in a simple approximation
as low pass behavior of the first order. Therefore, the low pass
filtering of first exhaust gas temperature TvK that is running in
monitoring device 17 may be approximated using a corresponding low
pass filter of the first order. The time constant of the low pass
filtering should be adjusted to the expected time constant of
component 18 that is to be monitored. The adjustment may be
calculated or may take place experimentally. At the output of the
low pass filter a signal is ready which, at least approximately, is
equivalent to second exhaust gas temperature TnK. A difference
formation between low pass filtered first exhaust gas temperature
TvK and measured second exhaust gas temperature TnK makes possible
a statement concerning whether the low pass behavior of component
18, that is to be monitored, has changed. By comparison of the
difference to a threshold value, stored in a threshold value memory
18, or a threshold band having an upper and a lower threshold, it
may be decided whether the change in the low pass behavior exceeds
the measure predefined by the threshold value or threshold band. If
so, error signal FS is emitted, which signals the change in the low
pass behavior of component 18 that is to be monitored. A change in
the low pass behavior occurs if component 18, that is to be
monitored, has been partially or completely removed, or has been
exchanged for another component having a higher heat capacity.
[0029] Another embodiment of the method according to the present
invention provides that a tolerance band be laid about first
exhaust gas temperature TvK, and subsequently a difference from
second exhaust gas temperature TnK is formed. If the ascertained
difference exceeds or undershoots a threshold value or a threshold
band that is stored in threshold value memory 18, emission of error
signal FS takes place. The tolerance band about first exhaust gas
temperature TvK may be formed in that a predefined temperature
amount is added and a predefined temperature amount is subtracted.
The amounts are selected in such a way that, in a component 18 that
is to be monitored according to the rules, second exhaust gas
temperature TnK lies within the tolerance band of first exhaust gas
temperature TvK at every point in time. A change in the low pass
behavior of component 18, that is to be monitored, leads to second
exhaust gas temperature TnK either leaving the tolerance band or
lying too far in the middle. If the difference formation between
the second exhaust gas temperature and the tolerance band exceeds
or undershoots the predefined threshold value or threshold band,
error signal FS is emitted.
[0030] Another embodiment of the method according to the present
invention provides a gradient formation of the two exhaust gas
temperatures TvK, TnK and a valuation of the gradient. A valuation
of the gradient may, for example, include the ascertainment of
maxima and/or minima, of both first exhaust gas temperature TvK and
second exhaust gas temperature TnK. An evaluation of a time
difference of maxima and/or minima between the two exhaust gas
temperatures TvK, TnK is a measure of the delay of second exhaust
gas temperature TnK compared to first exhaust gas temperature TvK,
based on the low pass behavior, by component 18 that is to be
monitored. A comparison of the time difference to a threshold value
stored in threshold value memory 18 or threshold band leads, if
indicated, to the emission of error signal FS.
[0031] A different valuation of the gradient is, for example, the
valuation of the amplitude of the gradient of first exhaust gas
temperature TvK in comparison to the amplitude of the gradient of
second exhaust gas temperature TnK. Based on the smoothing effect
of the low pass behavior of component 18, that is to be monitored,
the amplitude of the gradient of second exhaust gas temperature TnK
has to be lower than the amplitude of the gradient of first exhaust
gas temperature TvK. Another evaluation of the gradients is based
on a comparison of their averages.
[0032] An amplitude comparison is also possible directly between
first exhaust gas temperature TvK and second exhaust gas
temperature TnK, so that ascertaining the gradient may be omitted.
The ascertainment of differences between amplitudes as well as
directly between exhaust gas temperatures TvK, TnK and/or the
gradients of exhaust temperatures TvK, TnK has to be set to a fixed
time interval during the variation with time. The interval may
progress with time t, stepwise or continuously.
[0033] Still another embodiment of the method according to the
present invention provides a spectral analysis of the first and
second exhaust gas temperature TvK, TnK. The spectral analysis may
be done, for instance, by fast Fourier transformation FFT. Based on
the low pass behavior of the component that is to be monitored,
there is a shift in the spectrum of the first exhaust gas
temperature TvK from higher spectral components down to lower
spectral components at the second exhaust gas temperature TnK. A
comparison of the two spectral components is possible, for
instance, by forming the averages. In forming the averages, the
average frequency of the first and the second exhaust gas
temperature TvK, TnK is ascertained. The formation of the average
is equivalent to ascertaining the center of gravity of the plane
that is defined by the amplitude and the frequency.
[0034] By a formation of the difference and a comparison of the
difference to a threshold value or threshold band stored in a
threshold value memory 18, if necessary, error signal FS is
emitted.
[0035] Still another embodiment of the method according to the
present invention provides a correlation calculation of the first
exhaust gas temperature TvK to the second exhaust gas temperature
TnK. The resulting correlation coefficient may be normalized to the
quantity 1 if component 18, that is to be monitored, is not
present. In this case, one assumes the agreement of first and
second exhaust gas temperature TvK, TnK. On this assumption, in the
case of a component 18 that is to be monitored according to the
rules, the correlation coefficient has to have a predefined value
of less than 1. The method is described in Bronstein, Handbook of
Mathematics, Publisher Harry Deutsch, chapter 16.3.4 ff.
[0036] Yet another embodiment of the method according to the
present invention provides a correlation calculation of second
exhaust gas temperature TnK to the load and/or the torque and/or
fuel signal ME (the fuel injection quantity) of internal combustion
engine 10. The load and/or the torque and/or fuel signal ME of
internal combustion engine 10 are measures for first exhaust gas
temperature TvK. The load or the torque may be ascertained in
monitoring device 17, for example, from rotary speed signal N and
fuel signal ME or air-mass flow signal mL.
[0037] The advantage of this measure is that the variables named
are available in engine control unit 14 of internal combustion
engine 10, and only have to be evaluated.
[0038] The signal conditioning and the signal valuation of the
method according to the present invention may be completely
implemented as software. Monitoring device 17 as well as threshold
value memory 18 are preferably included in engine control 14.
* * * * *